Pre-tensionable sash balance



INVENTORS'. I GOT LARSON & HOWARD A. SMITH March 4, 1958 A. LARsoN ETALPRE-TENSIONABLE sAsH BALANCE v Original Filed Aug. 30, 1952 I, p 4 y l1FIG. I.

March 4, 1958 A. LAR'soN ET AL 2,825,089

' PRE-TENSIONABLE sAsH BALANCE original Filed Aug. so, 1952 l 2sheets-sheet 2 l .INVENTORS ALGOT LARSON 8 HOWARD A. SMITH f6 FlG.' 35f4 Ik 71W Armen/fw United States atcnt O l PRE-TENSIONABLE SASH BALANCEAlgot Larson, Stamford, Conn., and Howard A. Smith, Chicago, Ill.,assignors to Unique Balance Co., Inc., New York, N. Y., a corporation ofIllinois Original application August 30, 1952, Serial No. 307,232, nowPatent N0. 2,774,100, dated December 18, 1956. Divided and thisapplication October 17, 1956, Serial No. 618,418

6 Claims. (Cl. 16-197) The present invention relates to spiral-operatedspring sash balances and embodies more specilically an improvedstructure whereby the tension of the balance spring may be adjusted.

This application is a division of our copending United Statesapplication, Serial No. 307,232, tiled August 30, 1952 (now UnitedStates Patent 2,774,100, granted De cember 18, 1956).

Ever since the introduction of tubular spiral operated spring sashbalances attempts have been made to devise a suitable means forpre-tensioning the power spring of the balance mechanism to facilitatethe installation thereof and to insure the proper tensioning of themechanism for a desired operation. Installation is greatly simplifiedwhen the tension in the power spring of the balance mechanism closelyapproximates the load of the window sash since the balance mechanismneed then only be installed and does not require extensive adjustments.

Also desirable is an easy and simple means to make such minoradjustments of the power spring tension as might be required to reachthe final correct balance after installation or to correct changes inthe tension that might result from the use ot' the window. These minoradjustments must be capable of being made without disturbing thewoodwork or marring the nish of the frame or sash.

Past efforts (which employed ratchet mechanisms and other means) at thesolution of these problems have proven to be unsatisfactory. Some ofthese old means have required special tools or extra parts which wereeasily lost or mislaid and which were wasteful of labor and materials.

In those past attempts where ratchets were used to pre-tension and toadjust the tension of the power spring of the balance mechanism, theopposing surfaces of the ratchet mechanism have engaged in thehorizontal plane perpendicular to the plane of the tensile torce of thepower spring. The opposing surfaces of the ratchet mechanism were heldin engagement by the tension of the power spring, and as a suddenmovement of the window sash caused a sharp reduction in the tensionexerted by the power spring the opposing surfaces would becomedisengaged and the torsional force of the power spring thereby released.To overcome this defect, second vertical springs were employed in thebalance mechanism, but their purpose was solely to hold the opposingsurfaces of the ratchet in engagement and they did not aid in thebalance of the window sash. These supplementary springs were thereforeuneconomic and resulted in a more complicated balance structure.

The present invention accomplishes the above objects together with otheradvantages which will be more readily apparent from the followingdetailed description made with reference to the accompanying drawings.

ln the drawings: v

Figure 1 is a view in elevation taken on line 1-1 of Figure 2 of apreferred embodiment of the invention as Fatented Mar. 4, 1958 appliedto a window assembly, showing in partial -section the tubes and powerspring;

Figure 2 is a view in transverse cross-section taken on line 2 2 ofFigure 1 and looking in the direction of the arrows;

Figure 3 is a view taken on line 3-3 of Figure 1 and looking in thedirection of the arrows, showing the opposing surfaces of the ratchetmembers in engagement; and

Figure 4 is a view in partial section taken on line 4 4 of Figure l andlooking in the direction of the arrows, showing the convolute springholding in engagement the opposing surfaces of the ratchet mechanism;

Figure 5 is a cross-sectional view taken on line 5--5 of Figure 4 andlooking in the direction of the arrows; and

Figure 6 is a view in partial section showing the installed sashattachment plate and ratchet assembly, taken on line 6-6 of Figure 4 andlooking in the direction of the arrows.

Referring to the drawings, indicated at Figure 2 is a window frame 10and upper and lower sashes 11 and 12, respectively. For each of thesashes 11 and 12 there is provided a sash balance mechanism 13, whichmechanism is shown in greater detail in Figure 1.

The sash balance mechanism i3 comprises a tube 14 within which a coiledtorsion spring 15 is received. The upper end of the coiled spring i5 issecured to a sleeve 16, which together with the tube 14, is lixedlyattached to the frame itl by a drive screw 17 or other suitable means.Formed in the sleeve 16 is an inwardly directed detent 18. The coiledspring 15 is secured at its lower end to a nut 19 formed with a slot 20,within which is received a spiral rod 21. Spaced between the sleeve 16and the nut 19 and within the coiled spring 15 is a tube 22 made offibre or the like to eliminate noise which may be caused by the metal tometal contact during operation.

The balancing and lifting power of the balance mechanism 13, inaccordance with the Vconventional operation of this type of sashbalance, is dependent upon the tension of the coiled spring 15 which isvaried by the spiral rod 21. An equal lifting power at all points of therun of the sash 11 or 12 is maintained by the varying pitchY of thespirals of the rod 21.

The spiral rod 21 is attached in a slot 23 formed in a ratchet post 24by a hinge pin 25. The ratchet post 24 is received in an elongated slot26 formed in an offset end portion 27 of a sash attachment plate 2S. Thesashk attachment plate 28 is attached to the bottom of the sash 12 bydrive screws 29 and 30 or any other suitable means.

The sash attachment plate 28 is formed of sheet metal with the offsetend portion 27 having formed therein the elongated slot 26 which is ofsucient width to slidably receive the ratchet post 24. Also formedlatthe offset line of the sash plate 28 are a bent-up prong 31 and anopposing pawl 32. The opposing pawl 32 is not oiset, but is in the sameplane as the sash attachment plate 28 so as to coincide with notches 33spaced along the circumference of a head 34 of the ratchet post 24. Alsoformed in the head 34 is a slot 35 adapted to receive a screwdriver orother similar instrument. from the head 34 of the ratchet post 24 so asto allow a bearing surface 36 is an annular groove 37. Fitted in theannular groove is a convolute spring 33, the open end of which isengaged with the bent-up prong 31 of the sash attachmentlplate 23. Theconvolute spring 38 serves the dual purposes of locking the ratchet post24 in the elongated slot 26 and normally urging the opposing pawl 32 andthe notches 33 of the ratchet post head 34 into ,engagement whileallowing the lateral movement of the Spaced apart U ratchet post 24 inthe elongated slot 26 during adjustment of the balance mechanism 13.

The bent-up prong 31 receives the opened end of the convolute spring 3S`and also serves a a guide or stop to locate the sash attachment plate2i; against the sash, the prong 31 fitting against the inner edge of thesash grooves, as shown in Figure 6.

The balance mechanism 13 is pretensioned in the factory by withdrawingthe spiral rod 21 past the inwardly directed detent 18 in the sleeve 15and, while thesleeve 16 and tube 14 are held stationary, turning thesash attachment plate 2S and spiral rod 21 a predetermined number ofturns in the direction increases the tension in the coil spring 15. Thespiral rod 21 is then returned into the tube until the upper end of therod 2l passes the inwardly directed detent 18. The locking detent 13prevents the rotation of the spiral rod 21 thereby retaining the tensionimparted to the coiled spring 15.

The balance mechanism 13 is installed in the vertical grooves in thesashes 11 and i2 with the sash attachment` 28 pivoted so that it isparallel to the axis of the mechanism 13 and having its flat bottom sidedirected toward the frame jamb 10. The upper end of the mechanism 13 issecured at the head ofthe jamb iti by the drive screw 17. The lower sash12 is then raised to its highest elevation, at which position the end ofthe vertically pivoted sash attachment 28 should extend somewhat belowthe bottom edge of the sash 12. The sash attachment 28 and spiral rod 21is then pulled down to a point where the sash attachment plate 28 can bepivoted to a horizontal position and, with the bent-up prong 31 againstthe inner edge of the groove in the sash 12, attached t0 the lower edgeof the sash 12 by drive screws 29 and Sii. The distance between thelocking detent 1S and the top of the spiral rod 21, as indicated onFigure l, when the spiral rode 21 is fully advanced in the balancemechanisrn 13 is sufficient to allow a margin of safety in thisinstallation procedure.

This installation operation is repeated on the other side of the sash 12which then can be raised or lowered to any level desired. When the sash12 is lowered, the end of the spiral rod 21 passes below the lockingdetent 1S in the sleeve 16 and the arrested torsional tension in coiledspring 1S is released and will counter-balance the sash 12 at any point.

If after installation it is` necessary to increase the ten- .sion of thecoiled spring 15, the spiral rod 21 is turned in the direction whichincreases the tension by a screwdrlver inserted in the slot 35 in thehead 34 'of the ratchet post 24. The point of the pawl 32 as it slidesout of the ratchet notch 33 and 'along the circumference of the ratchetpost head 34 forces the ratchet post 24 back in the elongated `slot 25against the force exerted by the convolute spring 3?? until the pawl 32reaches the next notch 33 where the force of the convolute spring 33will urge the pawl 32 and notch 33 into engagement. This operation iscontinued until the proper increased tension is secured.

To reduce the tension in the coiled spring 15, external pressure isexerted against the ratchet head 34 to force it in the elongated slot 26away from the offset line so that the pawl 32 and the notch 33 aredisengaged. The torsion of the coiled spring 15 will turn the ratchetpost 24 until the next notch 33 is reached and the convolute spring 38forces the pawl 3?. and notch 33 into engagement. This process isrepeated until the desired tension of coiled spring 15 is secured.

From the foregoing it can be seen 4that factory pretensioning is a greatconvenience andsource ofleconomy of time and `labor to the buildingtrade. ri'he more ac-` curate pre-tension adjustment made by the workersskilled in the manufacture of the balance mechanism `lessens the dangerof destructive adjustment 'being made during installation. The easeandfacility with which adjustments may be made after installation withoutrnarrng' the woodwork or nish of the window is obvious from theforegoing.

While the invention has been described with reference to the specificstructure shown in the drawings, it is not to be limited save as in theappended claims.

We claim:

l. Window sash balance mechanism` comprising a tubular casing open atits lower end and adapted to be secured to a window jamb, a nutrotatably receivcdin the lower end of said casing and providing accessto thc hollow thereof through a slot centrally formed in said nut, ahelicai power spring nested in said casing and having opposite ends insecured relation with, respectively, said nut and said casing, saidspring opcrably being wound to urge rotation of said nut relative tosaid casing, a member fixedly connected to said casing and forming inthe hollow of said casing a detent disposed radially inward or saidspring and'axially intermediate the lower and upper ends of said casing,a spiral rod received in slidable relation in said slot to pass through.said nut up wardly into said casing to engage said detent when the rodis fully advanced into said slot and to disengagc from said detent whensaid rod is partially retracted from said casing, said engaged rod beingheld against rotation by said detent, and said held rod engaging thesides of said slotl to restrain said nut from the rotation urged by saidwound spring to thereby preclude said spring from unwinding, and meansto secure the lower end of said spiral rod to a window sash.

2. Mechanism as in claim l wherein said spiral rod, when fully advancedinto said slot, extends for a distance beyond said detent to permit apartial retraction of said rod from said casing through an initial rangeof retraction for which said rod remains in full engagement with saiddetent, said rod becoming disengaged from said detent by retraction ofsaid rod beyond said initial range.

3. Mechanism as in claim l wherein said nut as a tubular shank receivedin said casing and a head adapted to be seated on the rim of the lowerend of said casing, said shank serving to maintain said casing and nutin axial alignment during partial retraction of said nut and rod fromsaid casing.

4. Window sash balance mechanism comprising, a tubular casing open atits lower end and adapted to be secured to a window jarnb, a sleeve,inside the hollow of said casing, having an upper section in closefitting and secured relation with said casing and a lower taperedsection axially spaced from the lower end of said casing and forming anannular space between said casing and said lower sleeve section, saidlower section being characterized by a detent projecting into the hollowot said casing radially inward of said sleeve, a nut rotatably receivedin the lower end of said casing and providing access to the hollowthereof through a slot centrally formed in said nut, a helical powerspring nested in said casing and extending from an attachment, securingsaid spring in relation to said nut, upwards through the hollow of saidcasing into said annular space to an attach ment securing said spring inrelation to said sleeve and casing, said spring oper-ably being wound tourge rotation of said nut relative to said casing, a spiral rod rcceivedin slidable relation in said slot to pass through said nut upwardly intosaid casing to engage said detent when the rod is fully advanced intosaid slot, and to disengage from said detent when said rod is partiallyrc;` tracted from said casing, said engaged rod being held againstrotation by said detent, and said held rod engag ing the sides of saidslot to restrain said nut from the rotation urged by said wound springto thereby preclude said spring from `nnwiriding, and means to securethe lower end of said spiral rod to a window sash.

5. Window sash balance mechanism comprising, a tubular casing open atits lower end and adapted to be sccured to a window jamb, a nut having atubular shank rotatably received in the lower end otsaid casing and ahead adapted to be seated on the rim of said casing at said lower end,said nut providing access to the hollow of said casing through a slotcentrally formed in said nut, a sleeve, inside the hollow of saidcasing, having an upper section in close fitting and secured relationwith said casing and a lower tapered section axially spaced from thelower end of said casing and forming an annular space between saidcasing and said lower sleeve section, said lower section beingcharacterized by a detent projecting into the hollow of said casingradially inward of said sleeve, a helical power spring nested in saidcasing and extending from an attachment, securing said spring inrelation to said nut, upwards through the hollow of said casing intosaid annular space to an attachment securing said spring in relation tosaid sleeve and casing, said spring operably being wound to urgerotation of said nut relative to said casing, a spiral rod received inslidable relation in said slot to pass through said nut upwardly intosaid casing to extend beyond said detent when said rod is fully advancedinto said slot, said rod being adapted to engage with said detent whenso advanced and when retracted from said casing through an initial rangeof retraction, and to disengage from said detent when retracted beyondsaid initial range, said engaged rod being held against rotation by saiddetent, and said held rod engaging the sides of said slot to restrainsaid nut from the rotation urged by said wound spring to therebypreclude said spring from unwinding, and means to secure the lower endof said rod to a window sash.

6. Mechanism as in claim 5 further comprising a liber tube disposed insaid casing to axially lie between the lower section of said sleeve andthe tubular shank of said nut and to radially lie between said helicalspring and said spiral rod, said liber tube preventing noisy mechanicalcontact between said spring and rod.

References Cited in the ile of this patent UNITED STATES PATENTS 491,114Johnson Feb. 7, 1893 1,926,951 Larson Sept. 12, 1933 2,565,804 De Vrieset al Aug. 28, 1951 2,597,459 Dickinson et al May 20, 1952 2,604,655Peremi July 29, 1952 2,622,267 Peremi Dec. 23, 1952 2,774,100 Larson etal. Dec. 18, 1956

